Some foundations that are used to support various types of tower structures, such as a support tower structure for a wind turbine electric power generator, use a pier/mat foundation. The pier/mat foundation is used in an example to securely attach the tower of a wind turbine electrical generator to the physical ground and to maintain the security of the attachment in a wide range of atmospheric conditions including heavy and buffeting winds from any direction.
A pier/mat foundation generally consists of a gravity spreading mat that is in contact with and distributes support forces to the supporting ground. At least part of the gravity spreading mat is often below ground level. The gravity spreading mat in an example has a horizontal cross-sectional area that is large enough to distribute the anticipated load of an operating wind turbine electrical generator and its support tower to the ground.
The pier/mat foundation in an example has a pier placed on top of the gravity spreading mat. The pier is generally above ground level and generally has a smaller horizontal cross-sectional area than the gravity spreading mat. The support tower for the wind turbine electrical generator attaches to the top of the pier and the pier is generally secured to the gravity spreading mat by rods that extend through the pier into the mat. In some examples those rods are also used to secure the base of the support tower of the wind turbine electrical generator to the pier/mat foundation structure. Because of the different requirements for the pier and the gravity spreading mat, these two foundation components are generally fabricated separately. The combination of the pier/mat foundation includes a pier/mat interface where the two components join.
Certain pier/mat wind turbine foundations in some cases exhibit premature degradation due to deficient design which did not recognize fatigue induced in the foundation resulting from various wind loads of the wind turbine. These foundations over time can crack at the pier/mat interface and catastrophically fail, without warning, consequently destroying the entire wind turbine generator. Foundation repairs with very high costs in terms of money and down time may be incurred when the foundation exhibits critical degradation.